This patent application claims priority from U.K. Patent Application No. 0113971.6 filed Jun. 8, 2001, U.K Patent Application No. 0114805.5 filed Jun. 18, 2001 and U.K. Patent Application No. 0114912.9 filed Jun. 19, 2001.
This invention relates to a packing apparatus that is typically adapted for packing and/or supporting articles, such as pipes or pipe-work or equipment or machinery. The invention especially concerns damping of conductor tubes of offshore installations, such as fixed platforms, jack-up rigs and floating installations.
Many industrial structures and plant require a large network of pipes to convey fluids around the structure. In oil and gas plant, the large network of pipes requires a great deal of maintenance to control damage due to corrosion, erosion and fatigue. One particular problem associated with oil and gas plant is structural fatigue of pipes due to vibration. The vibration is generally unavoidable and typically results from the high-speed flow of fluid through the pipes, and on oil and gas platforms, it is general practice to support all pipes and pipe-work using structural supports. However, designing, making and installing these pipe supports is quite labour intensive, because the support brackets are generally fabricated in preset sizes, which may not precisely fit between a pipe and the nearest supporting structure. Therefore, in order to ensure a good fit between the pipe and the support bracket, shims are inserted on site between the pipe and the support bracket, so as to ensure that any space for vibration is minimised. Shims are also formed to pre-set sizes.
Drill conductor tubes in, for example, fixed offshore platforms run from the seabed up to the wellhead area passing through a series of guide tubes built into a steel jacket framework. The purpose of the conductor tube is to protect the high-pressure wellhead casing, which runs within it from environmental effects. The wellhead casing is guided within the conductor tube and hence the assembly moves laterally as a unit. The wellhead tree is attached to the top of the wellhead casing and is used for the connection of topside flowline pipework. The conductor and casing assembly acts as a tall slender structural element fixed at its base and carrying a large mass (the wellhead tree) at its top and having intermediate lateral guides in between.
The effects of wave and wind action are able to displace easily the conductor, which must then be restrained by the intermediate guides.
The conductors are installed after the jacket and topside structure by lowering the conductors through the jacket guides then grouting them into the seabed. The annular gap between a conductor and its guide tube must be sufficiently large to allow the conductor joint connectors to pass through and allow for misalignment of the guide tubes during fabrication of the jacket. The larger the gap the easier the conductors will be to install. However, a large gap will allow a conductor tube more freedom to move and hence cause large wellhead and flowline pipework movements. In addition, large impact forces will occur when the conductor tube contacts its guide tube.
Once the conductors are installed they can either have shims installed at the guides or they can be left free to move within the guides. In either situation problems can arise. If no shims are installed the conductors are free to move within the constraints of the guide tube. This should not affect the conductors or the guide tubes but the wellhead tree will experience larger than desirable movement and shock loading due to the conductor coming to an abrupt stop within its guide tube. This can cause large flowline pipework movement and vibrations, which can cause problems in the flowline pipework and attachments, in particular cumulative fatigue damage.
When shims are installed they tend to comprise steel strips forced down the annular gap between the conductor tube and its guide tube often completely eliminating any movement of the conductor tube. The practice of rigidly fixing the conductor tubes within the guide tubes is not recommended. Wave induced deflection of the conductor tube can induce large end moments if the conductor tube is rigidly fixed at its guide tube locations. The jacket guide tubes and framing members are generally not designed to resist these end moments. Local over stressing and fatigue problems can occur in the jacket structure if the conductors are rigidly fixed to the guide tubes.
An object of this invention is to provide a method and apparatus for packing or supporting articles, such as pipes, pipework, equipment or machinery.
According to the present invention there is provided a packing device comprising a container for containing a settable substance within the container.
Typically the container is flexible and/or deformable.
The container is typically placed between two items for packing purposes, typically so as to pack one item within the other and to limit the extent of movement of the one item within the other.
The settable substance is typically poured, injected or otherwise delivered into the container once the container is in place, and normally while the settable substance is in a liquid phase. After the container has been put in place and the settable substance has been delivered, optionally via a valve in the container, the viscosity of the settable substance then changes, so that the settable substance adopts a generally solid or at least a less fluid phase.
The viscosity of the settable substance delivered into the container can be varied, and although the viscosity of the settable substance is typically higher than the viscosity of the substance when initially delivered into the container, it is not necessary for the initial substance delivered to the container to be of low viscosity. For example, the initial settable substance delivered to the container could be a gel or a sol. Equally, while the viscosity of the substance once set is typically higher than when it is initially delivered into the container, the viscosity of the final set substance might also vary between applications, and in some embodiments could be a gel or a sol, while in other embodiments the final set substance could be a hard plastics material.
The compliance of the set substance can even be varied within the container, so that when the substance has set, the container has different zones of hardness. This is particularly useful where some pliability of the device is desirable in the immediate vicinity of the item to be packed so as to prevent some slight movement but so as to prevent excessive vibration or other movement beyond certain parameters. In such embodiments, the compliance of the substance disposed immediately against the item to be packed can be less than the compliance of the settable substance in other parts of the container, for example around the outside of the container, spaced apart from the item to be packed. This can be accomplished by different zones within the container containing different compositions of settable material, or by a gradient of compliance of the settable substance within the container.
The invention also provides a method of packing an item, the method comprising inserting a packing device between the item and an adjacent structural support, the packing device comprising a container, inserting a settable substance into the container and allowing or promoting a change of viscosity of the settable substance.
The invention also provides a method of supporting a pipe, the method comprising inserting an inflatable bladder between the pipe and an adjacent structural support so as to take free space between the pipe and the adjacent structural support.
The invention also provides a pipe support comprising an inflatable bladder.
Typically, the bladder is inflated with a fluid that is settable, i.e. a fluid that can adopt different phases.
Typically the settable substance is delivered into the container via a valve in the container, and sets hard over a period of time or when induced to set by a catalyst or the like. Typically the packing device assumes a shape when set that conforms to at least a part of the space between the item and the adjacent structural support, thereby occupying the space between the item and the support, and preventing or limiting movement of the item.
The settable substance can be a polymer such as polyurethane, and can be delivered to the container in liquid form, and then allowed to polymerise within the container.
The possible triggers for polymerisation of the substance can include time, heat, light and catalysts. The set substance typically has plastic and/or elastomeric properties, or can be completely hard. The hardness characteristics of the set substance can be adjusted by adjusting the density of cross-linking within the set polymer. This can be achieved, for example by adding cross-linking agents, or adjusting the characteristics of the feedstock isocyanates and alcohols. Indeed, the hardness, strength, stiffness, abrasion resistance, toughness, frictional coefficient, and other characteristics of the substance can be adjusted in the final set in accordance with the desired characteristics for each particular application, The addition of low-cost fillers to the injected substance can reduce the amount of the higher cost polymer required to fill the container and thereby reduce the cost of certain embodiments.
Fillers and fibres can be added to the material injected into the container to form a composite material for additional strength or other characteristics. The set material can be made fire retardant or resistant by the addition of certain materials. In certain embodiments, the device can incorporate intumescent material.
The container can be flexible and in preferred embodiments of the invention can comprise a bag or tube. The container can typically be in the form of a closed bag of generally rectangular or other shape although the precise shape of the bag is unimportant, as this can be fabricated to suit individual structures and/or spaces. However, generally rectangular bags can be inflated to adopt a wide variety of shapes that fill spaces between a large number of pipes and supports, thereby providing some flexibility, and reducing the need to carry a large number of different sizes of bags to suit individual circumstances. In certain embodiments, the container can initially take the form of an endless tube that can be sealed where desired on-site in order to fit within various spaces that are encountered. The material of the bag can be a plastics or rubber material, such as nitryl or butyl rubber, and in some preferred embodiments the material can be puncture resistant so as to resist puncture while the injected material is still in liquid form within the bag. Indeed, the container can comprise two skins in certain embodiments, with an inner skin to contain the polymer or other settable substance, and outer skin to resist abrasion damage and/or thermal damage or puncture by structural support.
It should be noted than puncture and abrasion resistance is only desirable in certain circumstances while the injected material is polymerising into a solid (or more solid) phase, after which point, abrasion damage or puncture to the bag or container does not affect the functioning of the device, as the packaging function is performed by the set material.
It should also be noted that it is not necessary for the bag to expand to fill the whole of the space available, and that the bag not need even expand to its full extent. It is sufficient for the bag to be capable of expanding to be disposed between the two items to be packed, and this can be achieved as easily when the bag is half full as when it is completely full.
The invention also provides a method of adjusting the position of a pipe or other item of equipment within a supporting structure, the method comprising inserting an inflatable bladder between the pipe and the supporting structure, and inflating the bladder to move the pipe relative to the supporting structure.
This aspect of the invention can be used to centre or otherwise adjust the position of pipes or other item of equipment within structural supports, or to pre-load pipes with force in a particular direction within a supporting structure, which is frequently required within oil and gas plant.
In certain embodiments, the inflatable bladder can have a valve and can be connected via a conduit to a hydraulic pressure source in order to adjust the pressure on the inflatable bladder. In certain embodiments, many different bladders are provided, and all may be connected, optionally via valves, to a manifold that controls pressure distribution to all of the bags or bladders in order to co-ordinate movement of the pipe, or pre-loading force.
In embodiments of the invention where the transmission of force is contemplated, the provision of bags or bladders with large surface areas is a particular advantage, as large forces can be applied to the pipes by such bags or bladders, with relatively little movement.
In typical embodiments, the bag or bladder is positioned adjacent to the pipe, but in certain other embodiments, the bag or bladder can be integrated into the pipe supporting structure, or disposed between the immediately adjacent pipe support, and a more distant hard point. For example, in certain preferred embodiments the bag or bladder is positioned immediately adjacent the pipe between the pipe and the cradle or saddle against which the pipe normally rests. However, in some other embodiment, the bag or bladder can form part of the cradle or saddle, or the leg of the cradle or bracket, or can be disposed underneath a duck foot.
The invention also provides a method of moving an item comprising placing a packing device against the item, inflating the packing device with fluid, and optionally allowing the fluid in the packing device to change phase.
Bags and bladders can be placed in horizontal and vertical or other planes in order to move the pipe or other item in such planes.
Certain embodiments of the invention reduce the need for on-site adjustments of shims. Devices can also be designed with frictional coefficients that reduce the need for shoes to be installed at pipework supports in order to reduce abrasion damage to the pipes causes by the pipework supports.
Certain embodiments can also provide a damping function to the packing supports. By specifying different hardness values for the polymer, the stiffness of the damping function can be tailored to suit each application. This is extremely useful for pipework made from long-lasting materials that can be subject to fatigue due to vibration damage.
According to the present invention there is provided a method of damping a conductor tube in a guide tube therefor comprising the steps of inserting a bag between the conductor and the jacket and filling the bag with a settable material to provide a resilient layer between the conductor and the guide tube.
The present invention also provides a damping device for use between a conductor tube and a guide tube therefor comprising a bag adapted and shaped for insertion between a conductor tube and its guide tuba and adapted to be filled by a settable material.
The bags used in the invention are preferably sized so as to end only over a portion of the periphery of a conductor tube. In practice it may be convenient to use say four bags to damp a conductor tube, the bags being generally evenly spaced about the conductor tube. Spaces between adjacent bags can then be used to insert temporary chocks between the conductor tube and its guide tube in order to centralise the conductor while the material introduced into the bags sets.
The bags are preferably made of a material that is substantially impervious to the settable material. Synthetic fabrics are preferred materials for the bags and preferably such fabrics are coated with synthetic material. For example, the bags may be made of reinforced nylon coated with PVC. The bags themselves are preferably capable of withstanding pressures of at least 2 bar. The bags may be made by joining appropriately shaped sections of fabric such as, for example, by stitching and/or ultrasonic welding.
The settable material may be any suitable synthetic material that can be poured, injected or pumped into a bag and then set to provide a resilient slab. It is also desirable that the material when set be resistant to chemicals and to seawater. It is believed that polyurethane may be a suitable settable material for use in the invention. The bags may be partitioned, whereby different filling materials may be used in different sections of the bag. That may allow use of a bulking material to form a core with more or less resilient material used in outer regions of the bag to provide the requisite damping effect. The hardness of various sections of the slab may be adjusted by the same means.
The bags of the invention preferably have not only a filling port but also a vent to allow displacement of air as the bags are being filled.
Guide tubes for conductor tubes generally comprise a lower cylindrical part and a flared upper part, which facilitates the insertion of a conductor tube through the guide tube. The bags of the invention preferably have upper and lower parts that when expanded correspond with the cross-sectional shape of the annular gap between the cylindrical conductor tube and its guide tube. Preferably the bags will be sized so as to extend below the guide tube and the lower ends of the bags will preferably be shaped so as to expand to form a lip or bulge along their bottom edge that extends outwardly of the guide tube. The top and bottom shaping of the bags is intended to produce a filled bag that is resistant to axial displacement. The bags may have on their surfaces that contact the conductor tubes a layer or coating of a friction reducing material to enable the conductor to move axially with minimal or no displacement of the bag. Such a friction reducing material may be, for example, PTFE.
In some situations, the guide tubes may also have a flared lower section, in which case the bags to be used therewith will preferably have a lower section with divergent opposed faces to result in a filled shape corresponding to the profile of the annular gap in the region of the lower flared section of the guide tube.
Filling the bags with settable material only is generally suitable for clearances between the conductor and guide of upped 50 mm. For larger clearances it may be desirable to include in the bag a core. The inclusion of a core will reduce the amount of settable material needed and will also provide shape retention and stiffness to the bag during setting. The core may be a solid or may include voids to alter damping characteristics. The core may be provide with passages therethrough to allow flow of settable material through the core for even spread of settable material around the core and to help fix the core. The core may be made of synthetic material and may be made from a foamed or expanded material, such as of polystyrene. The core will preferably be adhered to or otherwise fixed to a bottom wall of the bag.
As an alternative to providing a core within the bag, a similar effect may be achieved by including in the beg void pockets.
It may be desirable to provide the bags with means for locating same prior to filling. To that end it is proposed that the bags have one or more hooks, clamps or the like to locate over a top edge of the guide tube, The hooks or clamps may simply be attached to a top part of the bag. On the other hand it may be desirable to provide some rigidity to the bags to facilitate feeding them into the annular gap between the conductor tube and the guide tube, in which case stiffening rods or the like may be attached along sides of the bags, such as in pockets on the side edges of the bags, and clamps or hooks may be attached to ends of these rods, either to top ends or to both ends.